There are many processes for leaching base metals such as copper and nickel with ammoniacal leach liquors. An example of such a process is the so called, "Cuprion Process" which is disclosed in U.S. patent application Ser. No. 311,063 now abandoned entitled Recovery of Metal Values from Manganese Deep Sea Nodules, filed Dec. 1, 1972, the teachings of which are incorporated herein by reference. The disclosure of patent application Ser. No. 311,063 now appears in U.S. patent application Ser. No. 548,430 filed Feb. 10, 1975 which is a continuation-in-part of application Ser. No. 311,063.
When ores such as manganese nodules are leached in an ammoniacal solution, it is desirable to recover the carbon dioxide and ammonia from the leach liquor. A common method for recovering carbon dioxide and ammonia is to steam strip the aqueous raffinate. However, a disadvantage of steam stripping is that if it is done with metal values in the aqueous phase, the metals precipitate. Furthermore, such precipitates are considered troublesome to process further.
The present invention utilizes organic acids to extract the metals from the leach liquor. In the past organic acid liquid ion exchangers have not been useful for the extraction of copper, nickel, cobalt and similar metals from ammoniacal solution for several reasons. Firstly, the solubility of these acids becomes appreciable in alkaline media. Secondly, with metals such as copper bound in ammoniacal complexes, the strength of the complex is such that the organic cannot load the metal ion.